var name = "Jack";

var a = {
    name: "Lucy",
    say: function() {
        console.log(this.name)
    }
}

var fn = a.say;
fn()
a.say()

var b = {
    name: 'Mary',
    say: function(fn) {
        fn();
    }
}
b.say(a.say);
b.say = a.say;
b.say();

// Jack
// Lucy
// Jack
// Mary